Raptor Jesus refers to jokes conflating a velociraptor with Jesus Christ, either by photoshopping a raptor's head onto Jesus' or by having Jesus interact with a raptor. The joke was primarily popular on 4chan in the mid-late 2000s.
A strong influence contributing to the spread of Raptor Jesus its Uncyclopedia page, which creates biblical-style lore about the character. The page explains that "Raptor Jesus roamed the Earth back when God Himself was still only a teenager. His execution is thought to be the cause of the extinction of the dinosaurs, as God was mad at the Romans for aiding in His son's death." Encyclopedia Dramatica also documented him, including a prayer for him which goes "Our Raptor, Whose art is /h/entai, shopped be Thy face; Thy donations cum, The Game be won. On Earth as it is on 4-chan. Give us this day our daily lulz and forgive us our trolling as we forgive those who troll against us, and lead us not into faggotry, but deliver us from /fur/ries For thine is the Server, the Banhammer, and the WIN. Forever and ever… Amen."
There is a definition for the term on Urban Dictionary  added September 7th, 2006 by user f1r3wAll, gaining over 4,200 likes (shown below). There is also a slideshow of Raptor Jesus memes on YTMND.